21759497 has 2 divisors, whose sum is σ = 21759498. Its totient is φ = 21759496.

The previous prime is 21759487. The next prime is 21759499. The reversal of 21759497 is 79495712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12645136 + 9114361 = 3556^2 + 3019^2 .

It is a cyclic number.

It is not a de Polignac number, because 21759497 - 2⁶ = 21759433 is a prime.

Together with 21759499, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21759499) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10879748 + 10879749.

It is an arithmetic number, because the mean of its divisors is an integer number (10879749).

Almost surely, 2^21759497 is an apocalyptic number.

It is an amenable number.

21759497 is a deficient number, since it is larger than the sum of its proper divisors (1).

21759497 is an equidigital number, since it uses as much as digits as its factorization.

21759497 is an evil number, because the sum of its binary digits is even.

The product of its digits is 158760, while the sum is 44.

The square root of 21759497 is about 4664.7076006970. The cubic root of 21759497 is about 279.1791306927.

The spelling of 21759497 in words is "twenty-one million, seven hundred fifty-nine thousand, four hundred ninety-seven".